WO2013128696A1

WO2013128696A1 - Digital broadcast method

Info

Publication number: WO2013128696A1
Application number: PCT/JP2012/074196
Authority: WO
Inventors: 裕美藤田; 永山　英紀
Original assignee: Ｎｔｔエレクトロニクス株式会社
Priority date: 2012-03-01
Filing date: 2012-09-21
Publication date: 2013-09-06
Also published as: BR112014021149A2; US9357276B2; US20150163567A1; JP2013183248A; BR112014021149B1; JP5310892B2

Abstract

In this digital broadcast method, a TTS conversion processing unit (5) attaches a time stamp to each packet of an MPEG-2 TS (Transport Stream) and converts the MPEG-2 TS to an MPEG-2 TTS (Time-stamped Transport Stream). A group-forming unit (6) gathers a predetermined number of packets of the MPEG-2 TTS to form a group. A null packet removal unit (7) removes null packets from the group. A transmission unit (8) shifts the MPEG-2 TTS packets in the group from which null packets have been removed to the front, converts said MPEG-2 TTS packets into RTP (Real-time Transport Protocol) packets, and transmits the packets to a communication line (3).

Description

Digital broadcasting method

The present invention relates to a digital broadcasting method using a communication line.

In digital broadcasting using a communication line such as the Internet, when performing high-definition broadcasting (high-definition video information) using MPEG-2 TS (Transport Stream) in which video and audio are multiplexed, a required transfer rate is high (for example, 24 Mbps) For this reason, it is conceivable to delete information (Null packets, etc.) not directly related to the content to lower the transfer rate.

However, in the case of MPEG-2 TS constant bit rate (CBR) transmission, playback timing can be reproduced on the receiver side at a constant rate in an environment that is not affected by jitter or packet loss. Model. If null packets are deleted by this model and the average rate is lowered, it becomes difficult to receive transmission information.

On the other hand, there has been proposed a method of removing null packets after attaching a time stamp to each packet of MPEG-2 TS and converting it to MPEG-2 TTS (Time-stamped Transport Transport Stream) (for example, Patent Document 1). reference). The receiving side can accurately reproduce the playback timing using the time stamp in MPEG-2 TTS. Therefore, since the transmitting side can delete the null packet, the average rate of data transfer on the communication line can be substantially reduced.

JP 2007-104085 A

The MPEG-2 TTS data stream is converted into RTP (Real-time Transport Protocol) packets with headers attached to a group of a predetermined number of MPEG-2 TTS packets and transmitted from the transmission side to the communication line. In the past, null packets were deleted on the transmission side, and non-null MPEG-2 TTS packets were packed up to the upper limit of RTP packets. For this reason, variations occur in the timing of RTP packetization on the transmission side, and the reception side needs to secure a buffer to absorb variations in arrival times of RTP packets. Further, there is a problem that the delay time on the receiving side increases.

The present invention has been made in order to solve the above-described problems. The object of the present invention is to eliminate the need for an extra buffer on the receiving side, reduce the delay time on the receiving side, and average the rate of data transfer on the communication line. It is possible to obtain a digital broadcasting method capable of substantially reducing the image quality.

In the digital broadcasting method according to the present invention, the TTS processing unit attaches a time stamp to each packet of the MPEG-2 TS and converts it into MPEG-2 TTS, and the group configuration unit has a predetermined number of the MPEG-2 TTS. A step of collecting packets to form a group, a step of a null packet removal unit deleting a null packet from the group, and a transmission unit of the MPEG-2 TTS packet in the group from which the null packet has been deleted. Pre-packed, converted into RTP packets, and transmitted to the communication line.

According to the present invention, no extra buffer is required on the receiving side, the delay time on the receiving side can be shortened, and the average rate of data transfer on the communication line can be substantially reduced.

It is a figure which shows the digital broadcasting system which concerns on embodiment of this invention. It is a figure which shows the example of RTP packetization by the system of embodiment of this invention. It is a flowchart of the digital broadcasting method which concerns on embodiment of this invention. It is a figure which shows the example of RTP packetization by the system of the comparative example 1. FIG. 10 is a flowchart of a digital broadcasting method according to Comparative Example 1. It is a figure which shows the example of RTP packetization by the system of the comparative example 2. FIG. 10 is a flowchart of a digital broadcasting method according to Comparative Example 2. It is the figure which compared the example of RTP packetization by each system of Embodiment of this invention and Comparative Examples 1 and 2. FIG.

FIG. 1 is a diagram showing a digital broadcasting system according to an embodiment of the present invention. This system is divided into a transmitter 1 and a receiver 2. The receiver 2 receives the RTP packet transmitted from the transmitter 1 via the communication line 3 such as the Internet. The transmitter 1 includes a video / audio encoder (compression / multiplexing device) 4, a TTS processing unit 5, a group configuration unit 6, a Null packet removal unit 7, and a transmission unit 8.

FIG. 2 is a diagram showing an example of RTP packetization according to the system of the embodiment of the present invention. FIG. 3 is a flowchart of the digital broadcasting method according to the embodiment of the present invention. The digital broadcasting method of this embodiment will be described with reference to these drawings.

First, the video / audio encoder (compression / multiplexing device) 4 outputs MPEG-2 TS used for normal broadcasting. Here, in the MPEG-2 TS, a Null packet not including a video or the like is inserted in order to adjust the reproduction timing when the original video is encoded by a broadcasting station or the like.

Next, the TTS processing unit 5 attaches a time stamp to each MPEG-2 TS packet and converts it to MPEG-2 TTS. Specifically, the MPEG-2 TS is input to the TTS processing unit 5 (step S1), and the time information at the time of encoding received from the video / audio encoder (compression / multiplexing device) 4 is used as a time stamp for the MPEG-2 TS. (Step S2).

Next, the group configuration unit 6 adds an MPEG-2 TTS packet to the group (step S3). The group construction unit 6 repeats steps S1 to S3 until the predetermined number n of MPEG-2 TTS packets is reached (step S4).

Next, the group configuration unit 6 passes a group of n packets to the null packet removal unit 7. The Null packet removal unit 7 deletes unnecessary Null packets from a group of n packets. Specifically, the TS header to which the time stamp is attached is read (step S5), and the packet ID (PID) is checked (step S6). If the PID is “PID = 1FFF” meaning a Null packet, the TTS packet is deleted (step S7), and the process returns to step S5. On the other hand, if the PID is not “PID = 1FFF”, since the TTS packet includes valid information, the MPEG-2 TTS is added to the RTP payload portion (step S8). Steps S5 to S8 are repeated until n packets of MPEG-2 TTS included in one group are processed (step S9).

Next, the transmission unit 8 prepends the MPEG-2 TTS packet in the group from which the Null packet has been deleted, adds a header, converts the packet into an RTP packet, and transmits the packet to the communication line 3 (step S10).

Subsequently, the effect of the present embodiment will be described in comparison with Comparative Examples 1 and 2. FIG. 4 is a diagram illustrating an example of RTP packetization according to the method of the first comparative example. FIG. 5 is a flowchart of the digital broadcasting method according to Comparative Example 1. In the first comparative example, MPEG-2 TS packets are packed into one RTP packet up to the upper limit without distinguishing Null packets (steps S11 to S14). As a result, there is no variation in RTP packetization timing, and in the case of MPEG-2 TS CBR transmission, the reproduction timing can be reproduced on the receiving side in an environment that is not affected by jitter or packet loss.

On the other hand, consider high-definition broadcasting in digital broadcasting using communication lines such as the Internet. In high-definition broadcasting, the required transfer rate is high, and it is conceivable to delete a null packet in order to lower this, but it is difficult to reproduce the reproduction timing on the receiving side. Therefore, since the Null packet cannot be deleted, it is difficult to apply Comparative Example 1 to digital broadcasting.

FIG. 6 is a diagram showing an example of RTP packetization by the method of Comparative Example 2. FIG. 7 is a flowchart of the digital broadcasting method according to Comparative Example 2. In Comparative Example 2, a time stamp is attached to each packet of MPEG-2 TS, converted to MPEG-2 TTS, and transmitted to communication line 3 (steps S15 to S22). For this reason, even if the timing and order of MPEG-2 TTS packets received by the receiver 2 deviate from the transmission side, the receiver 2 can rearrange the packets at the correct timing and order. That is, the receiver 2 can accurately reproduce the reproduction timing and order by the time stamp in the MPEG-2 TTS. Therefore, since the transmitter 1 can delete the null packet, the average rate of data transfer on the communication line 3 can be substantially reduced.

However, in Comparative Example 2, the Null packet is deleted, and the non-Null MPEG-2 TTS packet is packed up to the upper limit of the RTP packet. For this reason, variations occur in the timing of RTP packetization on the transmission side, and the reception side needs to secure a buffer to absorb variations in arrival times of RTP packets. Furthermore, the delay time on the receiving side increases.

On the other hand, in this embodiment, a predetermined number of packets including Null packets are collected to form a group, and Null packets are deleted from the group and the remaining MPEG-2 TTS packets are left-justified. Convert to RTP packet. Thereby, since RTP packets are generated at regular intervals, no extra buffer is required on the receiving side, and the delay time on the receiving side can be shortened. Even if there is no non-null MPEG-2 TTS packet in one group, the RTP packet is generated only in that group. For this reason, the length of the entire RTP packet is not constant, but there is no problem in the specification.

FIG. 8 is a diagram comparing RTP packetization examples according to the respective modes of the embodiment of the present invention and Comparative Examples 1 and 2. In Comparative Example 1, the transfer load is large because the NTP packet is included in the RTP packet. In Comparative Example 2, the Null packet is deleted to reduce the transfer load, but the RTP packetization timing varies. Therefore, since the arrival interval of the RTP packet is not constant on the receiving side, an extra buffer is required and the delay time increases. On the other hand, in the present embodiment, the transfer load is at the same level as in Comparative Example 2, and the timing of RTP packetization is at the same level as in Comparative Example 1. Therefore, in this embodiment, no extra buffer is required on the receiving side, the delay time on the receiving side can be shortened, and the average rate of data transfer on the communication line can be substantially reduced.

DESCRIPTION OF SYMBOLS 1 Transmitter 2 Receiver 3 Communication line 5 TTS process part 6 Group structure part 7 Null packet removal part 8 Transmitter part

Claims

A step in which a TTS processing unit attaches a time stamp to each packet of MPEG-2 TS (Transport Stream) and converts the packet to MPEG-2 TTS (Time-stamped Transport Stream);
A group forming unit collecting a predetermined number of packets of the MPEG-2 TTS to form a group;
A step of a null packet removing unit deleting a null packet from the group;
A transmitting unit comprising a step of prepacking the MPEG-2 TTS packet in the group from which the Null packet has been deleted, converting the packet into an RTP (Real-time Transport Protocol) packet, and transmitting the packet to a communication line. A digital broadcasting method characterized by the above.